1. Field of the Invention
The present invention relates to the field of display techniques, and in particular to a driving circuit, a repair method thereof, and a display device.
2. The Related Arts
As the display technology progress, the use of electroluminescent devices, such as, organic light emitting diode (OLED) or quantum dots light-emitting diode (QLED), as the light source in active-luminescent display is more and more popular, as the approach provides the advantages of high emission efficiency, quick response time, high resolution and contrast, near 180° viewing angle, wide operation temperature range, and capability to realize flexible display and large-area full-color display.
OLED and QLED are both electroluminescent device driven by electric current; that is, when a current flows through OLED or QLED, the OLED or OLED illuminates, and the brightness is determined by the current flowing through the OLED or QLED. The majority of known integrated circuit (IC) only transmits the voltage signal, and the pixel driving circuit of the OLED display or QLED display must accomplish the task of translating the voltage signal into a current signal. The conventional pixel driving circuit usually uses a 2T1C structure, i.e., two thin film transistors (TFT) and a capacitor, to translate the voltage into current.
As shown in FIG. 1, a conventional 2T1C pixel driving circuit for driving electroluminescent device comprises: a first TFT T10, second TFT T20, and a capacitor C10. The first TFT T10 is a switch TFT, the second TFT T20 is a driving TFT, and the capacitor T10 is a storage capacitor. Specifically, the first TFT T10 has a gate connected to receive a scan signal Scan, a source connected to receive a data signal Data, and a drain electrically connected to a gate of the second TFT T20 and to one end of the capacitor C10. The second TFT T20 has a drain connected to receive a positive voltage VDD of a power source, and a source connected to receive an anode of the electroluminescent device (OLED or QLED); the electroluminescent device has a cathode connected to receive a negative voltage VSS of the power source; the capacitor C10 has one end electrically connected to the drain of the first TFT T10 and the gate of the second TFT T20, and the other end electrically connected to the source of the second TFT T20 and the anode of the electroluminescent device.
For the display based on the above pixel driving circuit, the electroluminescent device always stays in a light-emitting state during usage, which results in accelerated ageing of the electroluminescent device and shortening the lifespan of the electroluminescent device. Moreover, when the electroluminescent device is damaged, there exists no effective way for repair and leads to the damaged pixel unable to emit light, resulting in degraded display quality and dark spot.